I am cheap and lazy so I want to get maximum use from an 8 by 4 sheet of plastic without having to cut it into a thousand petals and still have it work with the rest of the design.
What I came up with will probably work for me.
But I wanted to share the method so that it can work for you, and perhaps for disaster relief too.
Step 1: Design of the parabolic curve
However the method is valid.
I will leave the image notes to explain things for the moment.
I start with the mirror straight across from the target ball because if you start anywhere else, it is hard to figure out how big your dish will be.
There are 2 ways to do the mirror angle.
The mirror is set up at half the angle of the light hitting the mirror and the light bouncing away from the mirror. The parallel lines method is much quicker than measuring angles but you need to check as errors creep in.
I never learned cad.
I am sure this will be perfected on computer aided design programs.
Step 3: Keeping the shape? How to do it?
Step 4: The completed half dish
More pictures of the process to follow soon. I think that spills from the pot will not affect the dish much because the dish is not underneath the pot. The pot is painted black and has a glass top.
Step 5: Mistakes made and lessons learned
In the past I have used wheat paste with success on cardboard with foil or mylar. But if you put it between mylar and corrugated plastic, it takes forever to dry. Mine went moldy before it dried. So another glue is required.
I am not happy with mylar. You must face the metalized side up towards the sun or it will corrode by reacting with the glue. (Perhaps 2 layers of mylar one on top of the other with the metalized sides pressed against each other would work better? And then just held on with pins? or something similar?
I plan to make another reflector and use aluminium foil as the reflector material in it. And compare them.
Maybe 1/4 size models would not be expensive to make?
If I can find someone in Victoria with an interest in this (and some spare time) maybe we can test the thing.
The bamboo. I added it as an afterthought. But because of the parabolic shape you could have the bamboo or plastic or metal tubing all cut to size with holes ready to join them to the corrugated plastic. It could really work well!
The 3 point linkage. I just welded an extra piece of metal to the chair leg. But it would better be put in an optimized position.
I will write in more mistakes later.
The next stage is to put it on equatorial mount and align the mount properly.